Stoker



W. MITCHELL Jan. 16, 1940.

STOKER Filed Dec. 24, 1936 3 Sheets-Sheet l INVENTOR.

ATToRN sY Jan. 16, 1940. w, THE 2,187,520

STOKER Filed Dec. 24, 1936 3 Sheets-Sheet 2 Jan. 16, 1940. w. MITCHELL STOKER Filed Dec. 24, 1936 3 Sheets-Sheet 5 ATToRNEY Patented Jan. 16, 1940 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to improvements in stokers, and more particularly to a stoker for feeding and delivering more or less pulverulent fuel into the combustion chamber of a heating apparatus.

Generally defined, an object of the invention is to provide an improved fuel stcker which is simple and compact in construction, and which is, moreover, highly efficient and flexible in operation.

Some of the more specific objects of the present invention are as follows:

To provide an improved stoker mechanism wherein there is a single set of driving gears, and I a single operating shaft as between the motor and the fan.

To provide a stoker mechanism having a highly eflicient and simple mode for insuring the flow of lubricant on and over the operating mechanism including certain gears.

To provide a stoker mechanism having means for driving the fuel feeding screw at different rates of speed, the driving arrangement further being such as to save in power consumption and in which there is no appreciable lost motion.

To provide a stoker mechanism wherein combustion can be accomplished for temporary periods without operating the fuel feeding screw and while the fan is still in operation.

To provide manual means for operating the fuel feeding screw when the automatic operating mechanism therefor is shut off;

To provide a motor mounting wherein the motor is elevated so as to remove it from damp zones, and such mounting providing for easy and ready alining of the motor and operating shafts.

To provide air-stream means for preventing the back flow of gas through the fuel feed pipe and into the fuel hopper.

To provide a fuel stoker wherein special means are arranged for cleaning the retort and for freeing the same of carbon deposits.

To provide a stoker which is formed of a number of sectional units for easy assembly or dismantling for repairs and adjustments, and wherein the retort is likewise of sectional formation to permit easy insertion of the same through i the ash door of a heating apparatus.

To provide a stoker wherein the hopper is of cylindrical formation to prevent clogging and having special means cooperating with the feed screw for breaking up large clumps of material or foreign matter to prevent damage to the moving and operating parts of the entire mechanism.

These and other objects and advantages will be apparent from the following detailed description.

A clear conception of an embodiment of the improved features, and of the mode of con- 5 structing and of utilizing stokers built in accordance with the invention, may be had by referring to the drawings accompanying and forming a part of this specification, in which like reference characters designate the same or sim- 10 ilar parts in the various views.

Fig. 1 is a perspective view of the improved stoker;

Fig. 2 is a fragmentary plan view of the same, slightly in perspective and with the cover of the hopper removed;

Fig. 3 is an exploded perspective view of the stoker showing the constituent units and sections thereof;

Fig. 4 is a vertical sectional view through the retort of the stoker and on a larger scale; indicated on line 4--4 of Fig. 3;

Fig. 5 is a fragmentary detail sectional view taken on line 5-5 of Fig. 4;

Fig. 6 is a fragmentary detail sectional view taken on line 66 of Fig. 4;

Fig. 7 is an end view of the stoker, slightly in perspective with the gear box cover removed and with other parts in section to show structural details;

Fig. 8 is a-horizontal sectional view taken on line 8-43 of Fig. '7;

Fig. 9 is a fragmentary vertical sectional view taken on line 9-9 of Fig. 7;

Fig.. 10 is an enlarged fragmentary view of a ratchet wheel section showing the manner in which a pair of dogs engage the same for driving purposes;

Fig. 11 is a fragmentary detail view of the outer end of the fuel feed screw shaft showing the application of a wrench thereto for manual operation of the screw; and

Fig. 12 is a top view of the showing in Fig. 11.

While the invention has been illustrated herein as being applied to a particular type of pulverized coal stoker, it is not intended to unnecessarily restrict the scope by such specific embodiment, and the novel features may obviously be more generally applicable to other types of stoker mechanisms.

Referring now more particularly to the drawings, it will appear that the improved stoker mechanism includes in general a retort I 5 adapted to be positioned within the lower portion of a heating apparatus; a fuel feeding conduit I6v within a fan housing 2|, and a gear box 22 interposed between the motor and blower housing.

As will appear most clearly from Figs. 1, 2 and 7 0f the drawings, the gear box 22 has adjustably mounted on an exterior end wall thereof, a bracket 24, and by means of slots and bolts, the bracket may be adjusted vertically and transversely and secured in a desired adjusted position. The horizontal plate portion of the bracket has mounted thereon the motor 20 which receives electricity from any convenient source (not shown). By means of bolts 25 and slots 26 in the horizontal portion of the bracket, said motor may be secured in adjusted position on the bracket. The motor has an inwardly extending motor shaft 21. The fan or blower housing 2| is mounted on the opposite end wall of the gear box 22 and encloses the blower 23 which is mounted fast on a rotatable blower shaft 28. The amount of air to be drawn into the blower'casing can be controlled by adjustable shutters 29.

The blower shaft 28 extends through the major portion of the upper end of the 'gear box 22, and the inner end of the blower shaft 28 is adapted to be alined with the adjacent end of the motor shaft, and such alining is readily accomplished by virtue of the adjustable mounting of the bracket 24 and the adjustable mounting of the motor 20. When said shafts are brought into proper alinement, the adjacent end portions of the same are adapted to be yieldingly coupled by means of a coupling arrangement shown most clearly in Fig. 8. These couplings include a disk element 30 mounted fast on the end of the shaft 21 which has a pair of diametrically opposed bosses 3| adapted to extend between diametrically opposed bosses 32 on a blower shaft coupling element 33. There is interposed between the coupling elements 30 and 33. a leather or rubber disk 34 which is secured to the bosses 32 of the element 33 and also to the bosses 3| of the element 30 by bolts 35. This mechanism provides for a driving connection between the shafts 21 and 28, and it permits of slight yieldability or resiliency to absorb shocks and tortional stresses.

The major portion of the blower shaft 28 is housed within an open oil trough 39 which is formed at its ends with bearing portions 31 to rotatably receive spaced portions of the shaft 28. It should also be observed that said shaft 28, within the oil trough 36, is formed with a worm portion 38 movable in an open or cut out portion 39 of the trough. The trough 36 is mounted on an inner wall of the gear box 22 by means of slotted ears 40 which are adjustably and clampingly engaged by bolts or studs 4|. By this means, the oil trough may be properly positioned relative to the alined and joined shafts 21 and 28.

Within the lower and major portions of the gear box 22, there are a number of movable and driving elements including a sectioned but integral ratchet wheel 42 and a worm wheel 43. It is intended that the lower portion of the gear box 22 contain an abundant supply of oil or lubricant and that said wheels 42 and 43 run therein. During movement of the worm wheel 43, oil is carried up thereby and is removed by the worm 38 which meshes with the worm wheel 43 through the opening 39 in the oil trough.

,mounted on each eccentric 46 is a dog,

Excess oil thus carried up and removed by the worm 38 runs into the interior of the oil trough 36. The bearing portions 31,are formed with openings 44 so that oil from the trough can run therethrough and lubricate the interior of the bearings and the shaft portions therein. Ultimately, the oil trough 36 will overflow and oil therefrom will splash down onto and lubricate moving parts and mechanism in the gear box 22 and excess overflowing oil will of course be caught in the lower portion of the gear box 22.

The worm wheel 43 is freely revolubly mounted on a stationary shaft 45. This shaft has loose thereon, but secured together and secured to a face of the worm wheel, a series of four eccentrics 46, with the enlarged portions of adjacent eccentrics being oppositely directed. Loosely the outermost dogs being indicated by the numerals 41 and 48 respectively, and the dogs inwardly thereof being indicated by the numerals 49 and 50 respectively. Each pair of dogs is adapted to be operated jointly with a connected but oscillatory relationship as between the dogs of each pair. For this purpose, the innermost dogs of each pair, dogs 48 and 50, have slotted portions 5| into which lugs 52 on the companion dogs extend. The companion dogs 41 and 49 are provided with ears 53 to which are pivotally connected the inner ends of latch arms 54 and 55. It will thus be seen that the dogs 41 and 48 operate jointly but in an alternating stepped manner, and the same is true of the dogs 49 and 59. This is because of their eccentric mounting and the fact that each dog is oscillatingly connected with its companion dog. However, by means of a latch 54 or 55, one or both pairs of dogs may be raised to and held in an inoperative position. As shown in Figs. 7 and 9 of the drawings, the outer pair of dogs 41 and 48 are in raised inoperative position, while the other pair of dogs 49 and 50 are in operative position. The inoperative dogs are held in this position by a hooked head portion 54 on the outer end of the arm 54 and ex tend through the top of the gear box and are supportingly engaged with a protuberance 58. The outer ends 54 and 55' of the latch arms 54 and 55 may be covered by a hinged enclosure 51 which is shown in raised position in Fig. 7.

The fuel feeding screw I1 is integral with and adapted to be driven by a shaft 58. This shaft also carries the two sectional ratchet wheel 42 within the gear box. Said ratchet wheel turns as a unit but the inner section 59 thereof has a different number of ratchet teeth thereon than does the outer section 69. The result of this ar rangement is that if the dogs 41 and 48 are in inoperative position, and the dogs 49 and 50 are engaged with the teeth of' the inner ratchet wheel section 59, the member 42 as a unit, and associated parts, will be driven at a different rate of speed than if the dogs 49 and 59 were out of action and the dogs 41 and 48 were drivingly engaging the teeth of the outer section 69. The unitary ratchet wheel 42 is connected to the shaft 58 by means of a hub 6| secured to the shaft by a transverse pin 62. The pin is of a nature so that it may break if the operating mechanism meets with any severe strains or if the screw l1 engages especially hard foreign material. This safeguard prevents the moving parts from being damaged in the event of the contingencies mentioned. The connection between the hub member GI and the ratchet unit 7 82 is effected by ears 88 extending into slots therefor in a face portion of the unit 42.

Under certain conditions. it may be highly desirable to operate the fuel feeding screw II by hand. This may be true when it is merely desired to turn the screw in a short distance or when readily combustible material for a temporary fire is to be quickly fed into the retort. When hand operation of the screw i1 is desired, both pairs of dogs are removed from engagement with the ratchet wheel unit 42, in the manner previously described. Then, the apertured end of an elongated crank or wrench 84 is applied to the projecting end of the shaft 58 against the outer face of the hub 8|. The inner side of the lower end portion of the wrench carries a pivotal pawl 88 adapted to selectively engage the successive teeth 88 on the hub member 8|. Hence, by moving the wrench ll back and forth, the shaft 88 may be manually turned in a predetermined direction.

Forwardly of the gear box 22 and having its lower end portion entered by the fuel pipe I8, is the hopper i8. Said hopper is of cylindrical formation and this prevents fuel clogging therein. The hopper is adapted to be filled with pulverized fuel through the open upper end thereof which is controlled by a hinged cover member 61. From Fig. 3 of the drawings, it will be observed that the hopper is of sectional formation to facilitate assembly. It comprises a bottom section which is connected with the pipes l6 and I8, and said bottom section is adapted to have seated thereon the cylindrical body which is retained on the bottom in assembled condition by the elongated vertical tie rods 88. The feed screw l1 operates in the lower portion of the hopper and also through the fuel supply pipe l8 which encloses the major portion of the screw. When the screw is driven, it conveys fuel at a predetermined rate of speed from the lower portion of the hopper to the inner fuel chamber 88 of the retort II. An agitator 10, in the form of a star wheel, is rotatably mounted in the bottom of the retort and is adapted to be turned by engagement with blades of the screw l1. This agitator serves to keep the fuel stirred up and prevents undue packing thereof. Formed on a bottom wall portion of the retort adjacent the forward end of the screw and in close proximity thereto is a steel chisel II. This member serves to cooperate with the screw in breaking large mass material or especially hard material which might of itself damage the blades of the screw.

In an upper wall portion of the hopper, there is a small opening 12 protected interiorly by an overhanging ledge 13, which opening communicates with a small exterior housing 14 into which the end portion of a vertical air pipe 15 extends. The other end portion of the pipe 15 extends to and communicates with the interior of the blower housing 2|. It should also be observed that between medial portions of the fuel feeding pipe l6 and the air pipe 18, there is a short circuiting conduit 16. During the operation of the stoker, when combustion is taking place, it may happen that gases of combustion may flow back through the pipe I8. The purpose of the connection I6 is to short circuit this gas and to cause it to be returned to the retort and combustion chamber of the heating apparatus through the air pipe 18, in which the direction of gas travel is toward the retort because of the force exerted by the blower 23. It'may happen, however, that the draught throught the pipe I8 is insufficient to cause a short circuiting of such returning gases, and in that event some may seep through the fuel into the retort. If ,this contingency occurs. such seeping gas will then be drawn into the blower housing via the pipe 15 and will ultimately be returned to the combustion chamber through the pipe i8.

The outer end of the fuel supply pipe l8 opens into a lower interior portion of the retort l5 and specifically said pipe is in communication with the lower reduced end portion of the inner fuel chamber 88 which is formed of two bolted-together half sections, as best shown in Figs. 3 and 4. Said chamber 88 is spacediy surrounded by a lower cylindrical retort section 11. The retort is built up to its proper height by an upper retort section I8 adapted to be superimposed on the lower section 11. It should also be observed that the fuel chamber 89 has superimposed thereon, within the upper retort section 18, and spaced from the inner walls thereof, a plurality of rings 19. Certain of said rings have depending lugs 88 for engagement with members therebelow to aid in the spaced superposed mounting of the rings. The relationship of the rings is such that air spaces 8| are formed therebetween.

During installation of the stoker, the retort is originally in the sectional condition shown in Fig. 3 and this permits easy insertion of the lower retort members through the ash pit door of the heating apparatus. After proper positioning of the lower retort members within the heating apparatus, the rings 19 are mounted in the manner shown in Fig. 4 and then the upper retort section 18 is mounted on the lower retort section 11. The retortsections I8 and 11 are secured together by means of depending wedging lugs 82 on the upper section II which, when the section 18 is properly turned, are adapted to wedgingly engage the inclined surfaces 83 on the retort section 11. Thereafter a pin 84 is dropped through an aperture in a lateral lug 85 to register with a proper aperture 86 in a properly positioned lateral lug 81 on the exterior of the lower retort section 11.

When the stoker is in operation and while combustion is taking place, air forced through the air pipe I8 is introduced into the lower portion of the retort section 11 exteriorly of the coal chamber 68 and this air then circulates upwardly and can pass into the space enclosed by the superimposed rings 18 through the slots or openings 8| to aid in combustion. Also, during operation of the stoker, ashes and carbon deposits may collect in the lower portion of the retort section 11 and against the walls thereof. It is desirable to keep this area relatively free of deposits which would restrict air flow. For this purpose, a slack chain 88 is normally disposed around the bottom portion of the retort section '11 and it is confined between the inner surface of the curved annular wall of the retort section and a curved inner partition 89. One end portion of said chain extends into the air pipe l8 and is connected to the inner end portion of an elongated rod 88, which rod extends through the major portion of the air pipe l8 and out of the adjacent lower portion of the blower casing 21 and is formed with an external head 90. Opening into the other side of the lower portion of the retort section 11 is a box or housing 9| into and through which the other end portionof the chain 88 extends. The extremity of said portion of the chain is attached to a removable cover 92 at the outer end of the box 9!. when it is desired to clean the lower portion of the interior of the retort or to free deposits on the walls thereof, the knob at the end of the rod 89, and the box cover 92, are grasped, and by alternately moving said members inwardly and outwardly, by virtue of the slack in the chain 88, the chain is given a back and forth oscillatory motion so as to scrape surfaces within the lower part of the retort,

It is believed that the mode of operation of the improved stoker will be apparent from the foregoing description. As has been heretofore suggested, pulverulent fuel from the hopper I9 is ultimately fed at a slow and steady rate to the upper portion of the interior of the fuel chamber 69 in the retort, where combustion takes place. Inasmuch as the retort is positioned within a heating apparatus, the heat from the burning fuel is utilized to raise the temperature of a heating fluid. structurally, the stoker has many advantages. As will be gleaned from Fig. 3 of the drawings, it is of sectional construction and comprises a number of easily secured together sections. This greatly simplifies installation and assembly problems, and also makes it easy to disassemble certain portions of the stoker for repairs or replacements.

With respect to the driving mechanism for the fuel feeding screw, it should be observed that a minimum of gears and operating parts are required, and these are associated in a novel, effective and efllcient manner. There is only a single, substantially unitary shaft between the motor and the fan or blower, and the motor is maintained in an elevated dry position and its proper alining with the blower and blower shaft is provided for. Because of the system of eccentrics 46 and the driving dogs operated thereby to engage proper sides of the wheel 60, there is a maximum use of the generated power, and no appreciable lost motion. This arrangement also makes it possible to operate the fuel feeding screw at different rates of speed. There is also the further advantage that direct power drive to the fuel feeding screw can be eliminated, and thescrew may be turned by hand in either direction to meet certain contingencies. The stoker is furthermore of simple and novel construction, and is well adapted for the purposes set forth.

What is claimed as the invention is:

In a power transmission apparatus, the combination with a feed screw, and a drive shaft, said power transmission apparatus being interposed between said screw and said shaft, of a worm on said drive shaft, a worm wheel driven by said worm, a worm wheel shaft, two pairs of connected dogs eccentrically mounted on said worm wheel shaft, a shaft extending from the feed screw, a pair of ratchet wheels fast on the last-mentioned shaft, the teeth of one wheel being coarser than those of the other, one of said pairs of connected dogs selectively engaging one of the ratchet wheels for driving purposes, and means for throwing one or both pairs of dogs into inoperative position out of engagement with said ratchet wheels.

WILLIAM MITCHELL. 

